The following disclosed invention relates to the art of handwriting recognition, signature identification and specifically to handwriting input devices.
The invention further relates to the art of generating writing and determining dynamics information thereof.
The invention still further relates to the art of automatically converting written text into handwriting dynamics information for use in handwriting recognition and signature authentication devices.
Automatic recognition of handwriting is a different problem due to the wide variability of appearance, registration, interrelationship between letters, and style differences between individuals. Attempts have been made to reduce the variability of written characters by identifying and extracting certain features which can be more easily associated with each letter. Other methods relying on the dynamics of the handwriting are used by including stylus to paper velocity and acceleration information in order to derive a better estimate of the character signal.
Many prior art handwriting recognition and signature authentication devices use dynamics information generated from a simultaneous writing apparatus. Such apparatus generally transmit signals associated with the writing such as stylus direction, velocity, or acceleration and largely depend on some physical paramter which stimulates an appropriate transducer. For example, U.S. Pat. No. 4,513,437 uses axial pressure of pen tip, U.S. Pat. No. 4,345,239 depends on acceleration related capacitance and U.S. Pat. No. 4,475,240 optically senses writing direction.
All of these devices derive dynamics dependent information by indirect means and they are limited to inexact approximations or ambiguous results. For example pen tip axial pressure will generate a signal even if the stylus is stationary, direction sensing will not indicate velocity or acceleration, and accelerometer type devices are not sensitive enough to accurately indicate the subtle changes in handwriting velocity. Furthermore, prior art stylus input devices discard much useful information since they are responsive only to a small number of handwriting parameters.
The present invention does not suffer from any of these limitations since a complete record of all spatial and dynamics information of writing is maintained and recorded by the disclosed method and apparatus without any loss of information. It has a greatly improved accuracy and lends itself to a much higher degree of reliability when used in combination with handwriting recognition and signature authentication algorithms.
Other more conventional means of writing input involve two-dimensional array devices such as x-y tablets, light pens in combination with CRT and the like for determining stylus position and dynamics. Most of these devices require direct connection to the handwriting processors and are cumbersome and costly. Furthermore, access to handwriting recognizers and signature authenticators are restricted to a collocation of input device and processor thereby limiting the number of users.
The present invention provides for a simple, small and portable input device allowing for practical remote use without the restriction of processor collocation.
The present invention discloses a method and apparartus for converting handwriting to writing dynamics information by using a code generating stylus for writing on a surface. Said code generating stylus modifies writing indicia by modulation of the writing markings thereby embedding time code information within the writing path. The writing image including the embedded code is then optically scanned, after-the-fact, resulting in a digital representation of the writing image. The digitized image is processed by resolving the spatial data back into the dynamics of orthogonal vertical and horizontal components by interpretaion of the code embedded in the writing.
The dynamics information together with the spatial image data can then be further processed by one of the multitude of pattern recognition/handwriting authentication analysis methods.
The disclosed device can also be used for recognition of uniquely defined symbols or for the recreation of the time sequence of isolated writing strokes for use as input control. For example, if said code generating stylus embeds time dependent code in the writing, successive strokes on a printed surface can be recreated in its originally written order. Writing strokes included on a page having menu commands or characters printed thereon can be used to recreate said menu sequence by associating the time/position of the stroke with the particular menu item. The detected command or character order could then be reproduced time sequentially.
A variation of the embedded time code allows for error detection and correction by providing the data with redundancy in accordance with one of the many methods known to those skilled in the art of error control coding (ECC).
Other variations of the present invention allow for embedding information other than time in the writing. Sensors built into the writing device can detect physical features of the user such as finger size, pulse rate, etc. for improving signature authentication reliability. Other information such as account numbers may be included in the embedded code such that a written signature may be cross referenced against user information.
A novel feature of the present invention is the ability of the system to ascertain the dynamic information from the writing after the writing is completed so that the only apparatus required in the writing process is the code generating stylus which lends itself to small size, portability, and versatility. The invention allows for conventional writing with the code generating stylus, the markings of which could then be later converted to typewritten text. The device would enable large numbers of users in an office environment to obtain typewritten papers directly from handwritten drafts without direct access to the handwriting processor. In field applications where access to a typewriter is impractical the present invention would serve as a pen size input device effectively producing the same results as a typewriter when the writing is later processed as disclosed.